How Many Decking Boards Do I Need?

To work out how many decking boards you need, measure your deck, multiply the length by the width for the area in square metres, then divide by the coverage of one board. Each of our standard boards covers 0.33m², so a 10m² deck works out at about 31 boards, or around 34 once you add 10% for waste. Add more for an awkward shape, and round up. The quickest way is to pop your measurements into the calculator on any board page, which does the sum and the wastage for you in one go.

Before you order, it helps to know roughly how many boards a deck takes, both to budget and to avoid coming up short halfway through. It is a simple sum once you know the size of a board, and there is a calculator on the site that does it for you. Here is how to work out how many decking boards you need, by hand and the quick way.

The quick way: use the calculator

On every board page there is a decking calculator. You put in the length and width of your deck and pick a wastage figure, 10% is the sensible default, and it tells you how many decking boards to order. It is the fastest and most reliable way to do it, because it uses the exact board size and rounds up for you. If you would rather understand the sum yourself, here it is.

Working it out by hand

Start with the area. Multiply the length of your deck by the width to get the square metres. A 4m by 3m deck is 12m². Then divide by the coverage of one board. Our standard boards are 2.2m long and 150mm wide, which covers 0.33m² each. So 12m² divided by 0.33 is about 37 boards. Add 10% for off-cuts and you are looking at around 40 boards. That is your order. It is worth checking the coverage on the product page for the exact board you choose, as it can vary slightly between ranges.

How many decking boards for common deck sizes

To give you a rough idea, here is how many of our standard boards common decks work out at, with 10% waste added:

These are for our standard 2.2m boards with a bit spare. Round up if your deck is an awkward shape or you are laying on the diagonal, which uses a few more.

Do not forget the frame and fixings

Boards are only part of the order. You will also need the joists for the subframe if you are not building in timber, the hidden fixing clips at a minimum of eight per board, the starter clips for the first row, and screws. If any of that is missing you cannot finish, so it is worth listing it all before you buy. Our decking kits bundle the boards and all the fixings together by the square metre, which takes the guesswork out for a straightforward rectangular deck.

A quick word on waste

The 10% figure is there for a reason. Every board you cut leaves an off-cut, and on a busy layout those add up. It is always cheaper to have a board or two spare than to stop the job and wait on another delivery, and a spare board is useful years later if one ever gets damaged. For a simple square deck you can drop to 5%, and for a complicated shape push it to 15%.

Once you have your number, you can order the boards on our composite decking boards page, or if it is a neat rectangle, compare it against a ready-made bundle on our decking kits page. Not sure? Send us your measurements and we will work it out with you.